砂粒粒径与砂层厚度对单体筐养养殖系统中三疣梭子蟹幼蟹摄食行为与生长特性的影响研究*     

徐永健  申屠基康  丁张妮 《海洋与湖沼》2015,46(1)

提要 在梭子蟹的单体筐养养殖系统中,试验了生态掩体(砂盒)中不同的砂粒粒径大小以及砂层厚度对梭子蟹幼蟹摄食行为与生长特性的影响。砂粒粒径设三个水平,分别为：>2 mm、<0.2 mm以及混合砂;砂层厚度有0cm、2cm、5cm、8cm四个水平。试验共进行6天,结果表明：砂粒粒径及砂层厚度对梭子蟹幼蟹的摄食与生长都有明显的影响。从砂粒粒径看,幼蟹在细砂(SPS)中挖洞休息,蟹体与砂面呈30-45°角,仅露眼睛及触角在外。一天内有3-6次进食,总进食时间为142.7±22.52 min,在摄食次数、总进食时间、平均摄食量(0.2427±0.0137 g/gBW)、以及脱皮及成活率都远高于其他粒径组,该组中幼蟹的体重增长最快,增加了0.814±0.113 g,增长率为91.5±3.43%;而该组的饵料系数(FCR)最低为1.17±0.11。因此,筐养养殖系统砂掩体的砂粒粒径最好为0.2 mm以下。砂层厚度也有类似结果,5 cm以上厚度养殖效果最佳。平均摄食量为0.2087±0.0046 g/gBW,该厚度下,幼蟹无死亡、100%脱皮,体重也增加最快,增加了0.791±0.121 g,增长率为88.9±3.74%,饵料系数(FCR)达到1.37±0.23,表明筐养系统掩体中砂层厚度要在5 cm以上。三种保护性酶类(SOD, POD, CAT)活性随着砂粒粒径变小和砂层厚度增加而降低,而消化酶类(淀粉酶、蛋白酶、脂酶)活性则表现与保护性酶类相反特性。从两类酶的活性变化也能证实,在优选条件下(细砂、厚度>5 cm),幼蟹所受的胁迫在降低。  相似文献   

3D Numerical Simulation Analysis of Passive Drag near Free Surface in Swimming     

詹杰民  李天赠  陈学彬  李毓湘  韦永康 《海洋工程》2015,29(2):265-273

The aim of this work is to build a 3D numerical model to study the characteristics of passive drag on competitive swimmers taking into account the impact of the free surface. This model solves the 3D incompressible Navier-Stokes equations using RNG k?ε turbulence closure. The volume of fluid (VOF) method is used to locate the free surface. The 3D virtual model is created by Computer Aided Industrial Design (CAID) software, Rhinoceros. Firstly, a specific posture of swimming is studied. The simulation results are in good agreement with the data from mannequin towing experiments. The effects of a swimmer’s arms and legs positions on swimming performance are then studied. Finally, it is demonstrated that the present method is capable of simulating gliding near the free surface.  相似文献   

Impact of different sampling rates on precise point positioning performance using online processing service     

Serdar Erol  Reha Metin Alkan  ?.Murat Ozulu  Veli Il?i 《地球空间信息科学学报》2021,24(2):302-312

In this study, the effect of different sampling rates (i.e. observation recording interval) on the Precise Point Positioning (PPP) solutions in terms of accuracy was investigated. For this purpose, a field test was carried out in ?orum province, Turkey, on 11 September 2019. Within this context, a Geodetic Point (GP) was established and precisely coordinated. A static GNSS measurement was occupied on the GP for about 4-hour time at 0.10 second (s)/10 Hz measurement intervals with the Trimble R10 geodetic grade GNSS receiver. The original observation file was converted to RINEX format and then decimated into the different data sampling rates as 0.2 s, 0.5 s, 1 s, 5 s, 10 s, 30 s, 60 s, and 120 s. All these RINEX observation files were submitted to the Canadian Spatial Reference System-Precise Point Positioning (CSRS-PPP) online processing service the day after the data collection date by choosing both static and kinematic processing options. In this way, PPP-derived static coordinates, and the kinematic coordinates of each measurement epoch were calculated. The PPP-derived coordinates obtained from each decimated sampling intervals were compared to known coordinates of the GP for northing, easting, 2D position, and height components. According to the static and kinematic processing results, high data sampling rates did not change the PPP solutions in terms of accuracy when compared to the results obtained using lower sampling rates. The results of this study imply that it was not necessary to collect GNSS data with high-rate intervals for many surveying projects requiring cm-level accuracy.  相似文献   

海洋微塑料对重金属的吸附行为及其复合毒性研究进展     

张晨曦  孙景春  林承刚 《海洋科学》2022,46(8):155-170

微塑料在海洋中的污染情况已经受到了人们广泛关注,但其与重金属相互作用产生的潜在生态风险依然需要进一步研究。本文主要综述了海洋中微塑料的来源及海水、沉积物和生物体内微塑料的污染现状,总结了部分海域微塑料上的重金属富集特征,并介绍了部分微塑料对重金属的吸附模型,最后总结分析了微塑料单独及与重金属协同作用对海洋生物的毒性效应。微塑料与重金属相互作用的结果依然存在许多不确定性,对生物体产生的毒性效应是协同、拮抗还是其他交互作用仍需更多的实验研究。本文旨在为评估微塑料与重金属相互作用造成的生态风险提供支撑,并为今后相关研究的开展提供参考。  相似文献   

气候变化感知对城市居民冰雪旅游环境责任行为的影响机制——以北京市为例     

王金伟  鹿广娟  张丽艳  曹淑婷  雷婷  孙洁 《地理研究》2023,42(2):440-457

冰雪旅游是推动冰雪经济与旅游产业高质量融合发展的重要途径,现已成为文旅产业中最具潜力的领域之一。然而在全球气候变化的影响下,冰雪旅游发展面临严峻挑战。文章以北京市为例,运用结构方程模型对冰雪旅游情境中城市居民的气候变化感知、感知价值、旅游意向和环境责任行为等变量间的影响关系及其形成机制进行分析。研究发现：(1)气候变化感知分为气候变化表征和气候变化风险两个维度,且两者显著正向影响冰雪旅游感知价值。同时,气候变化风险显著正向影响旅游者环境责任行为。(2)冰雪旅游感知价值显著正向影响冰雪旅游意向和环境责任行为。(3)冰雪旅游意向显著正向影响环境责任行为。(4)旅游经历在气候变化感知对冰雪旅游意向和环境责任行为的影响关系中具有显著的正向调节作用。本研究对厘清冰雪旅游情境下气候变化感知对游客环境责任行为的复杂影响机理具有重要的理论价值,同时也能够在一定程度上为相关部门把握“后冬奥”黄金机遇,推动冰雪旅游高质量发展提供决策参考。  相似文献   

Place Meanings and Participatory Planning Intentions     

Namyun Kil  Stephen M. Holland  Taylor V. Stein 《社会与自然资源》2014,27(5):475-491

Interest in integrating human connections and natural areas into resource management decision making has steadily increased. While efforts to validate place meaning dimensions have identified meanings beyond established place dependence and identity concepts, further research to identify tangible and intangible meanings of nature-based recreation areas is needed. This study sought to examine place meanings as a second-order construct consisting of ecological integrity, economic dependency, place dependence, family identity, community identity, and place identity and to determine the influence of place meanings on participatory planning intentions (PPI). Data were collected from Florida Fish and Wildlife Conservation area visitors. Confirmatory factor analysis revealed that six factors were reliable and valid, representing place meanings as an overarching concept. Structural equation modeling showed a significant association between place meanings and PPI. These findings demonstrated the importance of understanding place meanings that influence behavioral intentions, which is relevant to understanding participation in planning processes.  相似文献   

农业技术扩散中的农户采用行为研究:国外进展与国内趋势   总被引：3，自引：0，他引：3  

龙冬平  李同昇  于正松 《地域研究与开发》2014,(5)

农户是我国农区的微观经济单元,是农业技术采用的行为主体。以农户为对象的农业技术扩散采用行为的研究对于诱导农户行为、提高农业技术的采用效率、促进农区发展具有重要的理论和应用价值。从研究视角、研究方法、研究内容3个方面对国内外相关研究成果进行较为系统的梳理,总结评述最新进展和特点,并在此基础上对农户技术采用行为的研究趋势进行展望,希冀有助于推进国内对农户技术采用行为的深入研究,进而为促进农业技术扩散与推广、提高农业科技成果转化率提供参考。  相似文献   

芜湖高铁建设对居民出游行为影响调查及对策研究     

吉慧 《云南地理环境研究》2014,(5):35-39

从居民旅游交通决策行为、居民出游空间、居民出游行为预期影响3个角度分析芜湖市高铁建设对城市居民出游的影响.结果表明：（1）旅游交通是影响居民旅游决策的重要因素.（2）居民出游市场以近程为主,空间分布主要集中在100-400 km范围内,且东向出游特征明显,目的地以长三角地区为主.（3）高速铁路开通将增加芜湖居民出游交通工具的选择,改变原有的旅游市场空间,中远程出游比例增加,同时也会影响居民出游次数与天数以及景区的选择.最后,依据国内外学者对高铁旅游研究成果,结合本次问卷调查实际情况,初步探讨高速化背景下,芜湖市旅游的发展对策.  相似文献   

Evidence of marine mammal predation of the European eel (Anguilla anguilla L.) on its marine migration     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

Temperature and depth logging tags were implanted into adult eels released on Atlantic west coasts of France and Ireland to study their oceanic migration behavior. For three of the tags, 25 to 256 days after release there was a dramatic rise in temperature from 10 °C to 36 °C and the dive profile changed from depths of 300–1000 m to repeated ascents to the surface. This indicated that the eels carrying the tags had been eaten by a mammalian predator. Two of the tags had sufficient sampling rate to resolve the dives in detail. They recorded a total of 91 dives to maximum depths of 250–860 m lasting 11–12 min and with surface intervals of 5–7 min. More than two thirds of the dives included a rapid descent from approximately 500 m to 600–700 m. From this we infer that the predator was most likely a deep-diving toothed whale. The dives logged while the tags were inside the predator revealed that the temperature usually decreased during dives, and increased again during surface periods. The temperature drops during dives were probably caused by the ingestion of prey or water. These observations provide insights into the behavior of toothed whales foraging in the mesopelagic zone.  相似文献   

江西武宁县石门寺钨铜矿区风化作用过程中W、Cu等元素的表生地球化学行为(之一)     

胡小梅  龚鹏  李娟  闭向阳 《地质通报》2014,33(5):741-750

以江西省武宁县石门寺钨铜矿区燕山期和晋宁期岩体风化作用过程中W、Cu等元素的表生地球化学行为为研究对象,通过反映风化程度的化学风化指数CIA、风化作用过程中组分得失的估算、不同介质中W、Cu等成矿元素的含量变化及大离子亲石元素表生地球化学行为等方法的研究表明,石门寺钨铜矿区2个时期岩体元素淋失与风化强度有关,土壤剖面中碱金属、碱土金属元素大量淋失,而W、Cu等成矿元素在土壤B层中显著富集;从岩石到土壤、再到水系沉积物风化过程中,W、Cu等成矿元素含量逐渐升高,为此,一级水系沉积物和B层土壤是赣北九岭W、Sn、Cu、Mo多金属矿集区地球化学找矿的绝佳采样介质,是矿集区内找矿新突破的有效手段。  相似文献